4
Y1-03-0057 Rev. K
SECTION 1 – DESCRIPTION
The ACR/EM-2BA is a battery operated solid state megaphone specifically developed for use
in enclosed areas such as in the interior of an aircraft or ship cabin. It has been designed to
minimize regenerative acoustic feedback that results in whistling and other oscillations of this
nature. It has a 90° sound projection angle to direct the sound to persons in its immediate
vicinity, as well as in the rear sections of any aircraft. The amplifier frequency band-pass has
been selected to produce a crisp, clear reproduction of voice signals. The operating power
level is also sufficient to provide adequate sound under high ambient noise level conditions
without being over-powering. Specific attention has been given to the physical size so that
it can be used effectively in a crowded environment.
The integrated circuit amplifier only uses a small current when turned “ON”. This extends the
life of the batteries so that several hours of operation may be expected when used normally
in an intermittent manner. A simplified block diagram of the megaphone is shown in Figure
1 (shown below).
A battery test circuit is included. A flashing green LED indicates that the battery is Ok.
SECTION 2 – OPERATION
To test the battery, squeeze the handle and note if the green LED (located near the volume
control cap) is flashing. The batteries are useable as long as the LED flashes.
Hold the megaphone in one hand. Place mouth almost in contact with the microphone
mouthpiece at the rear of the assembly. Squeeze the handle, which will flex slightly, turning
the megaphone “ON” and speak slowly with loud, crisp, clear tones.
Adjust the volume control knob to a suitable sound level. The volume control may be adjusted
by removing the hole plug (4) and turning the potentiometer shaft inside the unit.
When not in use, carry the megaphone by the neck strap, attached to top of unit.
FIGURE 1
BLOCK DIAGRAM
ACR/EM-2BA PORTABLE SAFETY MEGAPHONE
VOLUME
CONTROL
MICROPHONE
ASSEMBLY
AUDIO AMPLIFIER
SIREN CIRCUIT &
BATTERY MONITOR
MEGAPHONE
SUB-ASSEMBLY
BATTERY
PACK
SPEAKER
ASSEM BLY
N.O.
N.C.
HANDLE
SW ITCH
+
+
+
-
-
-
